Validating commonly used drought indicators in Kenya

Abstract

Drought is a complex natural hazard that can occur in any climate and affect every aspect of society. To better prepare and mitigate the impacts of drought, various indicators can be applied to monitor and forecast its onset, intensity, and severity. Though widely used, little is known about the efficacy of these indicators which restricts their role in important decisions. Here, we provide the first validation of 11 commonly-used drought indicators by comparing them to pasture and browse condition data collected on the ground in Kenya. These ground-based data provide an absolute and relative assessment of the conditions, similar to some of the drought indicators. Focusing on grass and shrublands of the arid and semi-arid lands, we demonstrate there are strong relationships between ground-based pasture and browse conditions, and satellite-based drought indicators. The soil adjusted vegetation index has the best relationship, achieving a mean r 2 score of 0.70 when fitted against absolute pasture condition. Similarly, the 3-month vegetation health index reached a mean r 2 score of 0.62 when fitted against a relative pasture condition. In addition, we investigated the Kenya-wide drought onset threshold for the 3-month average vegetation condition index (VCI3M; VCI3M < 35), which is used by the country’s drought early warning system. Our results show large disparities in thresholds across different counties. Understanding these relationships and thresholds are integral to developing effective and efficient drought early warning systems. Our work offers evidence for the effectiveness of some of these indicators as well as practical thresholds for their use.

Effectiveness of Drought Indices in the Assessment of Different Types of Droughts, Managing and Mitigating Their Effects

“…To describe and indicate the aforementioned characteristics of drought, variables and drought indicators are required for their significant role in defining the level of drought reaction and timing, quantifying, monitoring, and detecting drought conditions [71]. Frequently, drought indicators are classified into two categories: meteorological indicators that include climatic parameters such as precipitation, temperature and evapotranspiration, and hydrological indicators that involve parameters such as streamflow, soil moisture and snowpack, groundwater, and reservoir levels [72,73].…”

Resilience and Adaptation Strategies in Response to Drought: A Spatial and Community-Based Study in West Pokot, Kenya

“…Most communities in the affected West Pokot County lack sufficient food reserves to survive until the next harvest, aggravating the depletion of pastures and water availability in the southern and eastern zones of the country. Vulnerable groups, particularly women, children, and the elderly in West Pokot, are the most affected, with the remaining healthy livestock either sold or permanently moved to areas with greener pastures, even across the border to Uganda [38,39].…”

A Screening Procedure for Identifying Drought Hot-Spots in a Changing Climate

“…Meteorological droughts over the Alps showed a shift towards prolonged events over the last two centuries [26] and are predicted to increase during the 21st century due to climate change [27], although it was suggested that the strength of a given drought signal strongly depends on the considered index [28] and that the use of different indexes might even lead to conflicting results [29]. Furthermore, droughts are complex phenomena, caused by a combination of events and pre-existing hydro-meteorological conditions, rendering the possibility to validate the use of any drought indexes or to set up warning systems based exclusively on observed data a very challenging task, especially in the case of large spatial domains [30]. A first attempt at compiling a systematic inventory of recorded drought events and climate evolution was recently made by an international consortium (ADO, ref.…”